She doesn't like revolvers? Rats...
The early series Rugers like the Police Service Six have smallish grips, have a great balance, are heavy enough to make .38's absolute pussycats, and are a bit smaller than K-frames in overall size. They're indestructible and cheap, too. $200-ish, usually.
But, 1) revolvers seem to be out, and 2) the Kaliforny Drop-test extortion racket means you'd have to hunt-up a private party sale, as Ruger would rather sell new guns than enable Kaliforny buyers to buy their used out-of-production products. Such is life in this stupid state. (No revos? Rats! .38's are so nice to shoot, even out of little guns.)
Hokay, next.
Blowback autos of all stripes have a couple of unpleasant aspects. They can have stiff recoil springs, making them difficult to rack the slide. A firm grip with both hands and a rolling or twisting motion with the shoulders can defeat this, but it'll take some practice. The next nastiest bit about blowbacks is their recoil. Even in small calibers, blowbacks can deliver a stinging slap to the hand when trhe slide stops against the frame. This can make them mighty unpleasant to shoot for newbies. The women that have tried my Makarov, or even my Colt 1903 .32, almost universally disliked the recoil characteristics. Smaller blowbacks are even worse, as they tend to sacrifice a bit of slide mass in the interest of staying small, which makes for even higher slide velocity and consequently worse recoil. Blowbacks are also at the bottom end of the power curve, topping out at the Makarov, which is basically equivalent to a stoutly loaded .380 auto. Makarovs are a bit big, but their mass makes them a tad more user-friendly. They're still pretty snappy though, and guns like the PA-63 can be downright nasty.
That would lead me to reccomend a locked-breech auto, even if it's in a large caliber. Locked breech enables a Kel-tec P-32 to be shootable even though it weighs a mere 6 ounces, while most .45's are eminently controllable by smallish folks. Unfortunately, most locked breech autos are more expensive, and tend to be biggish. 1911's are a good choice to consider, as they have a very slim profile that fits small hands well, with a short trigger reach. In the same vein, a Browning Hi Power has a very friendly grip, although it's double-stack mag can be a bit thick for some. Both of those usually cost a lot also.
Cz-75's, or the Witness series guns have a very comfortable grip, and the triggers are user friendly. They're double-stack guns, however, and fit would need to be verified. If they work, they're best buys in the market, coming in around $300 usually.
Kahrs, Glocks, and Sigs all cost a heap. I wish your girlfriend would just TRY shooting a Model 10 revolver (Rather than a snubby.) that has a nice trigger. I would say run it with both fore-fingers on the trigger. They are cheap, solid, reliable, and .38 is cheap enough for lots of practice. It's nicely effective, too. Police trade-ins abound, and most have very nice triggers.
I'm mostly wishing here, though. If revolvers are just not happening, so be it. Gun selection in Kaliforny stinks. I second the idea of trying out what you can find, but be weary of the blowbacks.